Technique for communication between user equipment and a data network in a communication network

ABSTRACT

A method for communication, in a packet-mode communication network, between user equipment and a data network. A session is established between the user equipment and a data-network access gateway via an access network. The method includes: detecting a request for access to a service based on at least one packet transmitted by the user equipment via the established session; a first step of determining, based at least one criterion, that a new session is to be established; a step of sending, to the user equipment, a control to establish a new session, the user equipment initiating establishment of the new session; a second step of determining another access gateway, the other gateway being suitable for the service required by the user equipment; and establishing the new session initiated by the user equipment, from which the new session is established between the user equipment and the other gateway.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Section 371 National Stage Application ofInternational Application No. PCT/FR2011/052787, filed Nov. 28, 2011,which is incorporated by reference in its entirety and published as WO2012/072929 on Jun. 7, 2012, not in English.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

THE NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT

None.

FIELD OF THE DISCLOSURE

The invention lies in the field of communication networks in whichaccess is performed in packet mode.

BACKGROUND OF THE DISCLOSURE

Evolutions of the UMTS (“Universal Mobile Terrestrial System”) mobilecommunication network standardized by the 3GPP organization are underdiscussion. These evolutions constitute the basis of a future fourthgeneration and are also called LTE (“Long Term Evolution”). Theyenvisage in particular an evolution of the core network EPC (“EvolvedPacket Core”) in which the exchanges are performed solely in packetmode. During its attachment to the mobile network, the user equipment UEestablishes a session with a packet data network and obtains an addressin this network. Thus, the user equipment possesses permanentconnectivity as long as it is attached to the mobile network. The userequipment UE is identified by an IPv4 address and/or by an IPv6 prefix.The packet data network is for its part identified by an identifier ofthe data network APN (“Access Point Name”). This session is also called“PDN connection”, PDN for “Packet Data Network”. Such a sessioncomprises at least one medium, called “bearer”, by default and cancomprise one or more dedicated media.

This session is established between the user equipment UE and the datanetwork by way of an access gateway P-GW. This access gateway P-GW isthe facility of the mobile communication network in charge of theinterface with the packet data network. A gateway P-GW can thus make itpossible to access services offered on the Internet communicationnetwork or else services offered by an operator.

An operator of the communication network may desire to have a certainflexibility in the choice of the access gateway as a function of aservice requested by the user equipment. It is not possible in thecurrent version of the standards to modify the access gateway P-GW,which has made it possible to establish a session.

SUMMARY

According to a first aspect, the subject of the invention is a method ofcommunication in a packet mode communication network between a userequipment and a data network, a session having been established betweensaid user equipment and a gateway for access to the data network by wayof an access network. This method comprises:

a step of detecting a request for access to a service on the basis of atleast one packet transmitted by the user equipment by means of theestablished session;

a first step of determining as a function of at least one criterion thata new session has to be established;

a step of dispatching to the user equipment a command regardingestablishment of a new session, said user equipment initiating theestablishment of the new session;

a second step of determining another access gateway, said other gatewaybeing suitable for the service requested by the user equipment;

a phase of establishment of the new session initiated by the userequipment, on completion of which the new session is established betweensaid user equipment and said other gateway.

The communication network is for example of the EPC type, for “EvolvedPacket Core” and comprises in particular the evolutions envisaged forthe core network within the framework of the LTE evolutions.

The data network can be the Internet public communication network orelse any other external data network, such as an Intranet network, or anetwork of an operator.

Access of the user equipment to the communication network can beperformed by way of various types of access networks. The access networkcan be radio or wire-based. The radio access network can comply with thesecond and third generation versions and also with the long-termevolutions of the third generation (LTE) that are defined by the 3GPPorganization. The access network can also be a non-3GPP radio accessnetwork, such as WIFI®, WiMAX, etc. access. The access network canfurther be an ADSL (“Asymmetric Digital Subscriber Line”) accessnetwork.

The communication method thus makes it possible to trigger establishmentof a new session on the initiative of the network but the actualestablishment of said session is initiated by the user equipment. Thenew gateway for access to a data network in packet mode has been chosenby one of the entities of the network so as to be suitable for theprovision of a requested service. It is thus possible to specialize theaccess gateways P-GW as a function of particular services. Thecommunication method thus makes it possible to distribute theestablishment of sessions relating to a service between a plurality ofaccess gateways.

It is also possible to establish the new session toward an accessgateway P-GW implementing certain particular functions, such ascharging, filtering, or control of service policies. It is thus possibleto implement quality of service policies differentiated as a function ofa charging level.

It is stressed here that the evolutions at the core network level withinthe framework of the LTE discussions do not envisage that an entity ofthe communication network can command the user equipment to establish asession. This makes it possible to limit the impacts at the userequipment level and to be compatible with the session establishmentprocedure initiated by the user equipment. Indeed, in such a network,the user entities possess permanent connectivity with the network. Thus,it is envisaged solely that the session establishment be on theinitiative of the user equipment. Moreover, for a 2G/3G packet corenetwork, the command procedure for activating a PDP context or a sessionis triggered when packets have to be routed to the user equipment. Itrequires that a static PDP information item be associated with the PDPaddress in order to be able to reach the user equipment and therefore,is not implemented in the communication networks. This procedure is usedhere in a different context from that for which it is envisaged, giventhat a session is already established and that it makes it possible toestablish a session to another access gateway.

It is also stressed that the communication method is compatible with theprocedures such as defined within the framework of the evolutions at thecore network level within the framework of the LTE discussions andrequire only limited modifications.

Operation at the user equipment level is also simplified since in oneembodiment, the user equipment need ascertain only a single APN datanetwork identifier. In this case, the network can, for its part, managedifferent data network identifiers and select a particular identifier asa function of criteria inherent thereto.

The detection of the request for access to a service on the basis of atleast one packet can be performed directly on the basis of the packet orelse indirectly on notification of the entity of the network havingreceived the packet.

According to a particular characteristic of the communication method,the criterion belongs to the group comprising an identifier of theservice, and an identifier of an application.

According to yet another particular characteristic, the detection stepis implemented by inspection of a packet stream associated with saidsession.

This inspection of the packets can be performed at various OSI levels.It can involve SPI inspection (“Shallow Packet Inspection”) at OSIlevels 3 or 4. It can also involve thorough inspection of the stream ofdata packets at OSI levels 7 and above or “Deep Packet Inspection”.

According to another particular characteristic of the communicationmethod, the other gateway is also determined as a function of at leastone item relating to the user equipment.

Advantageously, this item belongs to the group comprising an itemrelating to a location, an item relating to subscription data, and atype of user equipment.

Thus, it also makes it possible to choose an access gateway P-GW, whoselocation in the communication network is determined as a function of thelocation of the user equipment, in order to optimize the routing of thestreams of data packets, for example for a television service.

The user's subscription data make it possible to obtain a subscribedquality of service policy. The taking into account of this item thusmakes it possible to choose a suitable access gateway as a function ofthe subscribed quality of service. Given that it is possible toestablish the new session to an access gateway P-GW implementing certainparticular functions, such as charging, filtering, or control of servicepolicies, the implementation of quality of service policiesdifferentiated as a function of subscription data, and consequently of acharging level, is thus more easily implemented.

The type of user equipment makes it possible to select an access gatewayas a function for example of the generation of the terminal (2G, 3G,LTE), of the generation of the SIM card inserted into the terminal, etc.

The type of user equipment makes it possible to select an access gatewayas a function for example of the generation of the terminal (2G, 3G,LTE), of the generation of the SIM card inserted into the terminal, etc.

Advantageously, one of the two access gateways transmits a requestregarding establishment of a new session to a mobility managemententity.

This message is for example a “PDN Connectivity Request” message used onan interface between two entities of the network. It allows the mobilitymanagement entity to command the user equipment to establish the newsession. In one embodiment, the mobility management entity implementsthe second step of determining another access gateway, subsequent to thereceipt of the message originating from the network access gateway. Inother embodiments, the other access gateway is determined by an entityable to provide network policies, the latter initiating the creation ofsession to the other access gateway. The other access gateway thentransmits the “PDN Connectivity Request” message to the mobilitymanagement entity.

According to a particular characteristic, the access gateway with whichthe session is established implements the detection step and the firstdetermination step and transmits to the mobility management entity therequest regarding establishment of the new session, said mobilitymanagement entity then implementing the step of dispatching theestablishment command and the second determination step.

This implementation of the communication method is particularly suitablewhen the network does not comprise any entity able to provide networkpolicies.

When the communication network comprises entities for controllingnetwork policies and charging, the detection step and the firstdetermination step are implemented by an entity applying networkpolicies and,

an entity providing the network policies determines the other accessgateway and transmits to said other access gateway the request fortriggering establishment of the new session on the initiative of theuser equipment.

In this case, the other gateway for access to the network triggers theestablishment of the new session.

According to a second aspect, the invention also relates to a system ina packet mode communication network, designed to establish at least onesession between at least one user equipment and a gateway for access toa data network by way of an access network. This system comprises:

means for detecting a request for access to a service on the basis of atleast one packet transmitted by the user equipment by means of theestablished session;

first determination means, designed to determine as a function of atleast one criterion that a new session has to be established;

communication means, designed to dispatch to the user equipment acommand regarding establishment of a new session and to establish thenew session between the user equipment and an access gateway, said userequipment initiating the establishment of the new session;

second means for determining another access gateway, said other gatewaybeing suitable for the service requested by the user equipment.

According to a particular characteristic of the system, the userequipment is designed to receive a command regarding establishment of anew session and to process said request.

According to a third aspect, the invention also relates to a computerprogram comprising instructions for the implementation of thecommunication method according to the first aspect, implemented by anentity of the communication network, when this program is executed by aprocessor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood with the aid of the followingdescription of particular embodiments of the method of the invention,with reference to the appended drawings in which:

FIG. 1 represents the steps of the communication method according to aparticular embodiment of the invention;

FIG. 2 represents a packet mode communication network according to aparticular embodiment of the invention;

FIG. 3a represents the message exchanges and the steps of thecommunication method which are implemented according to a first variantof a first particular embodiment of the invention;

FIG. 3b represents the message exchanges and the steps of thecommunication method which are implemented according to a second variantof the first particular embodiment of the invention;

FIG. 4 represents the message exchanges and the steps of thecommunication method which are implemented according to a secondparticular embodiment of the invention;

FIG. 5 represents the message exchanges and the steps of thecommunication method which are implemented according to a thirdparticular embodiment of the invention;

FIGS. 6a, 6b, 6c represent entities of the communication networkaccording to particular embodiments of the invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 2 represents in a simplified manner a packet mode communicationnetwork 2. A user equipment UE 1 is represented in its environment. Theuser equipment 1 can access, in packet mode, data networks 30, 32 by wayof various types of access networks. Considered here is the particularcase where the communication network 2 complies with an EPS architecture(“Evolved Packet System”), such as specified in 3GPP standard TS 23 401v8.11.0. It is stressed here that the versions corresponding to“Release” 8 are mentioned subsequently. No limitation is attached tothis Release number, the communication method also being applicable tothe subsequent versions of these standards.

The access network can be radio, complying or not with thespecifications defined by the 3GPP standardizing organization, or elsewire-based.

A first type of access network corresponds to a second-generation 2G orelse third-generation 3G radio access network. In this case, radioaccess is performed by way of a GERAN entity (“GSM/EDGE Radio Accessnetwork”) for 2G radio access, or else of a UTRAN entity (“UMTSTerrestrial Resource Access Network”) for 3G radio access.

A second type of access network corresponds to an LTE, for “Long TermEvolution”, radio access network corresponding to the evolutions of thethird generation, also called pre-4G. In this case, radio access isperformed by way of an E-UTRAN entity, for “Evolved UTRAN”.

These first two types of access networks comply with the set ofspecifications defined by the 3GPP standardization group.

A third type of access network groups together the set of accesses notcomplying with 3GPP. The third type of radio access network is linked toan access node entity AN 14. This is for example a wire-based access ofADSL type, a WIFI® radio access, WiMAX for “Worldwide Interoperabilityfor Microwave Access”, CDMA, etc.

The first two types of access networks are linked respectively tomobility management entities. For 2G/3G radio access, such an entity 10is called SGSN, for “Serving GPRS Service Node”. For LTE radio access,such an entity 12 is called MME, for “Mobility Management Equipment”.These two mobility management entities are linked to an attachmentgateway 16 S-GW, for “Serving Gateway”. They are also linked to a serverof the subscribers of the network HSS 28, for “Home Subscriber System”,this server storing the set of subscription data for the subscribers ofthe communication network 2.

The attachment gateway 16 and the access node entity 14 are linked totwo access gateways P-GW1 and P-GW2. The access gateway P-GW1 22 makesit possible to access the first data network 32 in packet mode. Theaccess gateway P-GW2 20 makes it possible to access the second datanetwork 30 in packet mode. By way of example, the first data network 32corresponds to the IP data network and allows access to services ofInternet type. The second data network 30 corresponds to a data networkspecific to an operator and allows access to services offered by thisoperator. Application servers AF 26 and 27, for “Application Function”,are also represented in FIG. 2. The application server AF 26 makes itpossible to provide a service to the user in the data network 30. Theapplication server AF 27 makes it possible to provide a service to theuser in the data network 32.

It is also envisaged in an optional manner that entities of thecommunication network 2 implement a PCC (“Policy Control and Charging”)network policies and charging control. Such a communication network 2then comprises a PCEF (“Policy and Charging Enforcement Function”)policies application function, and a PCRF (“Policy and Charging RulesFunction”) rules provision function. In FIG. 2 is represented an entityfor providing PCRF rules 24. The latter is connected to the two accessgateways 20, 22. In this case, these latter implement the PCEF function.The communication network 2 can also comprise the implementation ofpolicies and charging control rules (PCEF function) in the absence of aPCRF entity.

Of course the communication network 2 represented in FIG. 2 comprisesonly a limited number of entities represented so as not to overload thisfigure. No limitation is attached to this representation. It is alsostressed that the attachment gateway S-GW and one of the access gatewayscan be grouped together in one and the same entity.

Hereinafter, an association between a user equipment UE, represented byan IPv4 address and/or an IPv6 prefix, and the packet data network,represented by an APN (“Access Point Name”) data network identifier, iscalled a session or connection to a packet data network. This sessioncan equally well be called an “IP-CAN session”, “PDN Connection” for LTEaccess, or “PDP Context” for 2G/3G access.

The method of communication between a user equipment UE and a datanetwork will now be described in conjunction with FIG. 1 in a firstembodiment.

In a first step E1, more precisely in a sub-step E11, a gateway P-GW1for access to a packet data network receives data packets originatingfrom the user equipment UE by means of a first established session. Thisfirst session has been established between the user equipment UE 1 andthe access gateway P-GW1 22 for example during the attachment of theuser equipment to the communication network 2. No limitation is attachedto the mode of establishment of this first session. The first session isestablished by way of the attachment gateway S-GW 16. Still in thisfirst step E1, the access gateway P-GW1 22 detects that at least one ofthe data packets received comprises a request for access to a given newservice.

Detection that this is a request for access to a given service can becarried out according to various variants:

according to a first variant, this may involve inspection of a stream ofdata packets at OSI levels 3 or 4, also called SPI for “Shallow PacketInspection”. In this case this entails an IP and TCP (“TransmissionControl Protocol”), or UDP (“User Datagram Protocol”), data packetsinspection; more precisely, detection can consist in detecting a givenIP destination address and a given destination port;

according to a second variant, this may also involve thorough inspectionof the stream of data packets at OSI levels 7 and above or “Deep PacketInspection”.

In a sub-step E12, the access gateway P-GW1 22 then determines that itis necessary to establish a new session between the user equipment UE 1and another access gateway allowing access to a packet data network as afunction of at least one criterion. This criterion can correspond forexample to an identifier of the service or else an identifier of anapplication. The access gateway P-GW1 22 then transmits a requestregarding establishment of the new session with the user equipment UE 1.This request comprises a specific indicator, for example an identifierof the service. More precisely, this establishment request istransmitted to the attachment gateway S-GW 16, which transmits it in itsturn to the mobility management entity SGSN/MME 10, 12.

In a step E2, more precisely in a sub-step E21, the mobility managemententity SGSN/MME 10, 12 receives the request regarding establishment ofthe new session with the user equipment UE 1 and determines a packetdata network identifier as a function of the specific indicator, byconsulting for example a DNS (“Domain Name Server”) database. Moreprecisely, the mobility management entity SGSN/MME 10, 12 interrogatesthe DNS database on the basis of an APN data network identifier and ofthe specific indicator and obtains in return the same or anotheridentifier of the APN data network.

In a sub-step E22 of step E2, one of the entities of the networkcommands an establishment of this new session between the user equipmentUE 1 and destined for the data network identifier determined in sub-stepE21, this establishment of the new session being on the initiative ofthe user equipment.

In a sub-step E23 of step E3, on receipt of a request regardingestablishment of the new session emitted by the user equipment, themobility management entity SGSN, MME 10, 12 determines another accessgateway as a function of the specific indicator by consulting forexample the DNS database. More precisely, the mobility management entitySGSN/MME 10, 12 interrogates the DNS database on the basis of the APNdata network identifier and of the specific indicator and obtains inreturn the other access gateway P-GW2 20. Optionally, one or more itemsrelating to the user equipment can also be taken into account whenchoosing the other access gateway P-GW2 20. This item can correspond toan item relating to a location of the user equipment. The choice of thisother access gateway suitable for the location of the user equipmentthus makes it possible to decrease the load in the network. It can alsoinvolve an item relating to user equipment subscription data, therebymaking it possible to select an access gateway with a service levelsuitable for the subscription. It may further entail a type of the userequipment.

The entity of the network implementing this step E2 is specifiedsubsequently in conjunction with the descriptions of FIGS. 3a , 3 b.

In a second embodiment, entities of the network implement a PCC (“PolicyControl and Charging”) network policies and charging control.

In such a second embodiment, the access gateway P-GW1 22 comprises aPCEF policies application function and implements step E1 previouslydescribed. The request regarding establishment of a new session is thentransmitted to the entity implementing the PCRF provision function. ThisPCRF entity 24 then implements sub-steps E21 and E23 and invokes themobility management entity SGSN, MME so that the latter commands (E22)the user equipment UE 1 to establish the new session. This secondembodiment is described more precisely in conjunction with FIG. 4.

In a third embodiment, an application server AF 26 receives the datapackets originating from the user equipment UE 1. The application serverAF 26 then provides the PCRF entity 24 with a message of service-relateditems. This message is received during sub-step E11. The entityimplementing the policies control function then implements step E1,sub-steps E21 and E23 and invokes the mobility management entity SGSN,MME so that the latter commands (E22) the user equipment UE 1 toestablish the new session. This third embodiment is described moreprecisely in conjunction with FIG. 5.

In these various embodiments, sub-step E21 is optional. In this case, itis possible to use a default APN data network identifier. It is alsopossible to implement sub-step E23 of determining another access gatewaybefore sub-step E22 of dispatching a command regarding establishment ofa new session.

The first embodiment will be described more precisely in conjunctionwith FIGS. 3a and 3b . FIG. 3a corresponds to access of the userequipment UE by way of an E-UTRAN access network. FIG. 3b correspondsfor its part to access of the user equipment UE by way of a GERAN orUTRAN access network. The variant applicable to a non-3GPP accessnetwork is not described in an explicit manner but the communicationmethod is also transposable to this type of access network.

More precisely, considered here is the particular case where thecommunication network does not implement an architecture comprising aPCRF entity. However, this does not exclude in such a network theimplementation of policies and charging control rules of PCC type.

FIG. 3a describes the exchanges between the various facilities for theimplementation of the communication method according to the firstembodiment in a first variant, that is to say in the case of an E-UTRANaccess network.

As described previously in conjunction with FIG. 1, the access gatewayP-GW1 22 receives data packets originating from the mobile entity UE 1,detects a request for access in at least one packet, determines that anew session has to be established and transmits a request regardingestablishment of the new session to the mobility management entity MME12 by way of the attachment gateway S-GW 16. In this first embodiment,the establishment request is a message M1 “PDN Connectivity Request”comprising in particular the following parameters:

a packet data network APN identifier to which the user equipment desiresaccess;

an identifier of the IP version requested “PDN Type”, that is to sayIPv4, IPv4v6, IPv6;

items intended to be transmitted destined for the user equipment UE 1 ina transparent manner, grouped together in an information field called“Protocol Configuration Options”;

a type of request “Request Type”.

These various parameters are coded in accordance with the codingenvisaged in 3GPP standard TS 23.401, paragraph 5.10.2, for a “PDNConnectivity Request” message when it is emitted by the user equipmentUE.

According to the invention, the message M1 “PDN Connectivity Request”also comprises a specific indicator, for example an identifier of theservice.

During this step E2 previously described in conjunction with FIG. 1,more precisely in sub-step E21, the mobility management entity MME 12receives the message M1 “PDN Connectivity Request” and performs a DNSdomain name resolution request to a DNS server, not represented in FIG.2. The mobility management entity MME 12 interrogates the DNS server onthe basis of the APN data network identifier and of the specificindicator and obtains in return an APN data network identifier,identical or different from that provided, suitable for the servicerequested. It is stressed here that this interrogation of the DNSdatabase can also make it possible to obtain another network accessgateway suitable for the service requested, as described subsequently.

When the APN data network identifier is not present in the “PDNConnectivity Request” message, the mobility management entity MME 12determines prior to the resolution request an APN data networkidentifier on the basis of a default subscribed PDN context.

The DNS server determines an APN data network identifier suitable forthe service requested and in return provides the mobility managemententity MME 12 with an APN data network identifier, identical or not.

The mobility management entity MME 12 then verifies as a function of thesubscription data for the user equipment UE 1 that the APN data networkidentifier provided by the DNS server is authorized and if such is thecase, the mobility management entity MME 12 uses for the following stepsthe APN data network identifier provided.

In sub-step E22 of step E2, the mobility management entity MME 12 thentriggers a phase of establishing this new session between the userequipment UE 1 destined for the APN data network identifier.

More precisely, the mobility management entity MME 12 dispatches to theuser equipment UE 1 a message M1 a “Request PDN Connectivity” commandingestablishment of a new session. This message M1 a comprises theinformation items previously described in conjunction with the messageM1 “PDN Connectivity Request”. However, the packet data network APNidentifier has been replaced with the one that was determined in stepE21.

It is recalled that such a session establishment command messagetransmitted from an entity of the network to a user equipment is notenvisaged within the framework of the LTE evolutions. Indeed, the userequipment possesses a permanent connectivity with the communicationnetwork. The need to process a request for transmitting data destinedfor the user equipment in packet mode, identified for the generationsprior to the LTE, has been deemed thus obsolete.

It is stressed here that according to the invention, the establishmentof this new session is commanded by one of the entities of the networkbut the actual establishment of said session is on the initiative of theuser equipment.

The 3GPP standard TS 23.401 “LTE; General Packet Radio Services (GPRS)enhancements for Evolved Universal Terrestrial Radio Access Network(E-UTRAN) access”, v8.11.0 specifies in particular in paragraph 5.10.2in conjunction with FIG. 5.10.2-1, the exchanges between the variousfacilities of the network in response to a PDN connectivity requestinitiated by the user equipment.

The user equipment UE 1 transmits to the mobility management entity MME12, by way of the access network, a message M1 b “PDN ConnectivityRequest”, requesting the establishment of a PDN session destined for thedata network identified by the data network identifier provided by themobility management entity MME 12 in the message M1 a.

In a sub-step E23, on receipt of this message M1 b, the mobilitymanagement entity MME 12 determines the other access gateway P-GW2 20 tothis data network as a function of the service requested. Moreprecisely, the mobility management entity MME 12 interrogates the DNSserver on the basis of the APN data network identifier and of thespecific indicator and obtains in return the other access gateway P-GW220.

An item relating to the user equipment can also be transmitted to theDNS server and thus taken into account when choosing the other accessgateway P-GW2 20. As indicated previously, this may be an item relatingto a location of the user equipment, an item relating to user equipmentsubscription data or else an item relating to a type of the userequipment.

It is recalled here, as described previously, that this determination ofthe other access gateway P-GW2 20 can also be carried out during theinterrogation of the DNS server in sub-step E21 so as to obtain both theAPN data network identifier and the other access gateway.

The new session will then be created at the network entities level. Themobility management entity MME 12 creates a message M2 “Create SessionRequest” and transmits it to the attachment gateway S-GW 16. The lattertransmits in its turn a message M3 “Create Session Request” to theaccess gateway P-GW2 20. If dynamic control of policies and charging isimplemented, the access gateway P-GW2 20 talks to the PCRF entity 24 inan exchange M4 “IP-CAN Session Establishment/Modification”. Next, oncethe new session has been created, the access gateway P-GW2 20 transmitsthe response in a message M5 “Create Session Response” destined for theattachment gateway S-GW 16. The attachment gateway S-GW 16 then returnsa message M6 “Create Session Response” to the mobility management entityMME 12. This set of exchanges is performed in accordance with paragraph5.10.2 of the standard TS 23.401 and is not detailed here.

Next, in a step E3, the mobility management entity MME 12 establishesthe new session toward the user equipment UE 1. This set of exchanges isperformed in accordance with paragraph 5.10.2 of the standard TS 23.401when it is initiated by the user equipment and is modified to implementthe invention. The mobility management entity MME 12 transmits a messageM7 “PDN Connectivity Accept” destined for the user equipment UE 1contained in a control message S1_MME “Bearer Setup Request”. The latteris destined for the E-UTRAN access network, the latter comprising aneNodeB entity. According to the invention, the message M7 “PDNConnectivity Accept” comprises in particular an indication thatestablishment has been commanded by the network. The eNodeB entity thentransmits a message M8 “PDN Connectivity Accept” contained in a message“RRC Connection Reconfiguration” destined for the user equipment UE 1.According to the invention, the user equipment UE 1 is in particulardesigned to receive the message “PDN Connectivity Accept” comprising theindication that it is emitted on the initiative of the network. The userequipment UE 1 uses the parameters received in the message M8 “PDNConnectivity Accept” contained in the message “RRC ConnectionReconfiguration” to update an association between the service requestedand an EPS medium. For this purpose, the user equipment UE 1 relies onfilters of level 3, 4 (TFT) or 7 to update this association. Once thereconfiguration has been performed, the user equipment UE 1 transmits amessage M9 “RRC Connection Reconfiguration Complete” destined for theeNodeB entity. The latter transmits in its turn a message M10 “BearerSetup Response” destined for the mobility management entity MME 12.Next, the user equipment UE 1 transmits a message M11 “Direct Transfer”comprising a message “PDN Connectivity Complete” destined for the eNodeBentity. The latter then transmits the message M12 “PDN ConnectivityComplete” to the mobility management entity MME 12.

The message M12 is received in a step E4 by the mobility managemententity MME 12.

According to the invention, the mobility management entity MME 12 thentransmits a message M12 b “PDN Connectivity Response” destined for theattachment gateway S-GW 16. The attachment gateway S-GW 16 transmits inits turn the message M12 b destined for the access gateway P-GW1 22. Themessage M12 b is received by the access gateway P-GW1 22 in a step E5.This terminates the procedure requesting establishment of a new session,which was triggered by the access gateway P-GW1 22 during step E1.

In parallel, subsequent to the receipt of the messages M10 “Bearer SetupResponse” and M12 “PDN Connectivity Complete”, the mobility managemententity MME 12 transmits a message M13 “Modify Bearer Request” destinedfor the attachment gateway S-GW 16. The messages M13 a “Modify BearerRequest”, M13 b “Modify Bearer Response” are exchanged if appropriatewith the access gateway P-GW2 20 in accordance with 3GPP standard TS23.401.

The attachment gateway S-GW 16 transmits in response a message M14“Modify Bearer Response” to the mobility management entity MME 12.

The mobility management entity MME 12 thereafter transmits a message M15“Notify request” destined for the server HSS 28, this message comprisingin particular an identifier of the access gateway P-GW2 20 and theassociated APN data network identifier. The server HSS 28 stores theseidentifiers in association with the user equipment UE 1 and transmits amessage M16 “Notify Response” destined for the mobility managemententity MME 12.

On completion of these various steps and exchanges of message, the newsession is established between the user equipment UE 1 and the accessgateway P-GW2 20 in conjunction with the APN data network identifier.The access gateway P-GW2 20 has been selected as a function of aspecific indicator, for example the service requested, and ifappropriate, as a function of items relating to the user equipment UE 1.The establishment of the new session has been initiated by the userequipment but by command of one of the entities of the network, moreprecisely in this first embodiment by command of the mobility managemententity MME 12.

FIG. 3b describes the exchanges between the various facilities for theimplementation of the communication method according to the firstembodiment, in a second variant, that is to say in the case of aGERAN/UTRAN access network. In this case, the session is also called a“PDP context”.

As described previously in conjunction with FIG. 1, the access gatewayP-GW1 22 receives data packets originating from the mobile entity UE 1,detects a request for access to a service, determines that a new sessionhas to be established and transmits a request regarding establishment ofa new session to the mobility management entity SGSN 10 by way of theattachment gateway S-GW 16. The establishment request is a message N1“PDN Connectivity Request” analogous to the message M1, describedpreviously in conjunction with FIG. 3 a.

During step E2 previously described in conjunction with FIG. 1, themobility management entity SGSN 10 receives the message N1 “PDNConnectivity Request” and performs the processings described inconjunction with FIG. 3a , in order to obtain an APN data networkidentifier.

In sub-step E22 of step E2, the mobility management entity SGSN 10 thencommands the establishment of the new session on the initiative of theuser equipment UE 1 and destined for the APN data network identifier.

Recall that 3GPP standard TS 23.060 “GPRS; Service Description; Stage2”, v8.10.0 specifies in particular in paragraph 9.2.2.2 in conjunctionwith FIG. 67 the exchanges between the various facilities of the networkallowing a GGSN gateway node entity to trigger a procedure foractivating a PDP context by the mobility management entity SGSN. Thisprocedure for activating a PDP context is on the initiative of the GGSNgateway node entity, on receipt of data to be transmitted destined forthe user equipment UE. The gateway node transmits for this purpose amessage “PDU Notification Request” to the mobility management entitySGSN. It is recalled here that a GGSN gateway node corresponds to acombination of the functions of the attachment gateway S-GW and of thegateway for access to a data network P-GW.

Thus, this procedure, such as envisaged in the standard, does notenvisage a modification of the GGSN gateway node which has transmittedthe message “PDU Notification Request”. Thus, the exchanges describedhere rely on this procedure but modifications are made to the latter toimplement the invention. According to the invention, the establishmentof this new session is initiated by the user equipment but is commandedby the implementation of step E2 at the level of the mobility managemententity SGSN, once the data network identifier has been determined.

More precisely, the mobility management entity SGSN 10 transmits amessage N2 “Request PDP Context Activation” destined for the userequipment UE 1, so that the latter initiates the establishment of thesession, that is to say of the PDP context requested. According to theinvention, the mobility management entity SGSN 10 also transmits amessage N3 “PDN Connectivity Response” destined for the attachmentgateway S-GW 16. The attachment gateway S-GW 16 transmits in its turnthe message N3 destined for the access gateway P-GW1 22. The message N3is received by the access gateway P-GW1 22 in a step E5. This terminatesthe procedure requesting establishment of a new session, which wastriggered by the access gateway P-GW1 22 during step E1.

The user equipment UE 1 uses the parameters received in the message N2“Request PDP Context Activation” to update an association between theservice requested and a medium. For this purpose, the user equipment UE1 relies on filters of level 3, 4 (TFT) or 7 to update this association.Once the reconfiguration has been performed, the user equipment UE thentransmits a message N4 “Activate PDP Context Request” destined for themobility management entity SGSN 10. In a sub-step E23, on receipt ofthis message N4, the mobility management entity SGSN 10 determines theother access gateway P-GW2 20 to this data network as a function of theservice requested. More precisely, the mobility management entity SGSN10 interrogates the DNS server on the basis of the APN data networkidentifier and of the specific indicator and obtains in return the otheraccess gateway P-GW2 20.

An item relating to the user equipment can also be transmitted to theDNS server and thus taken into account when choosing the other accessgateway P-GW2 20. As indicated previously, this may be an item relatingto a location of the user equipment or else an item relating to userequipment subscription data.

It is stressed here that this determination of the other access gatewayP-GW2 20 can also be carried out during the interrogation of the DNSserver in sub-step E21 to obtain both the APN data network identifierand the other access gateway.

The mobility management entity SGSN 10 thereafter establishes the newsession with the access gateway P-GW2 20. Once the latter has beenestablished, the mobility management entity SGSN 10 transmits a messageN5 “Activate PDP Context Accept” to the user equipment UE 1.

On completion of these various steps and exchanges of message, the newsession is established between the user equipment UE 1 and the gatewayfor access to the data network P-GW2 20 in conjunction with the APN datanetwork identifier. The access gateway P-GW2 20 has been selected as afunction of the specific service requested and if appropriate, as afunction of items relating to the user equipment UE. The establishmentof the new session has been initiated by the user equipment but bycommand of one of the entities of the network, more precisely in thisfirst embodiment by command of the mobility management entity SGSN 10.

The second embodiment will be described more precisely in conjunctionwith FIG. 4. FIG. 4 describes the exchanges between the variousfacilities for the implementation of the communication method accordingto the second embodiment, in the case of an E-UTRAN radio accessnetwork. FIG. 4 is readily transposable to an access of the userequipment UE 1 by way of the GERAN or UTRAN radio access network. Thevariant applicable to a non-3GPP access network is not described in anexplicit manner but the communication method is also transposable tothis type of access network.

More precisely, considered here is the particular case where thecommunication network implements an architecture with a PCRF entity toensure the PCC policies and charging control.

As described previously in conjunction with FIG. 1, during step E1, theaccess gateway P-GW1 22, implementing the PCEF function, receives datapackets originating from the mobile entity UE 1, detects a request foraccess to a service and determines that a new session must beestablished. The access gateway P-GW1 22 then transmits a requestregarding establishment of a new session to the PCRF entity. Moreprecisely in this case, the establishment request corresponds to amodification request for the session. In this second embodiment, themodification request corresponds to a message O1 a “Indication of IP-CANSession Modification” requesting a modification of the IP-CAN session.In accordance with 3GPP standard TS 23.203 v8.11.0, paragraph 7.4.1 andFIG. 7.4, this message O1 a comprises the following parameters:

an information field “Event report”;

an information field “affected PCC rules” comprising control rules forthe PCC policies affected.

According to the invention, this message O1 a “Indication of IP-CANSession Modification” also comprises:

an identifier of the PDN session or connection concerned, if saididentifier is available;

the specific indicator, for example the identifier of the service;

the address in the network of the attachment gateway S-GW.

During step E2 previously described in conjunction with FIG. 1, the PCRFentity 24 receives the message O1 a “Indication of IP-CAN SessionModification” and correlates the policies control rules with the IP-CANsession and the specific indicator.

The PCRF entity 24 verifies that the session between the user equipmentUE 1 and the access gateway P-GW1 22 is not suitable and decides toestablish a new IP-CAN session. On the basis of data associated with theservice, the PCRF entity 24 determines the most suitable access gateway,in the example described here the other access gateway P-GW2 20 and anAPN data network identifier as a function of the specific indicator. ThePCRF entity 24 also verifies the subscription data associated with theuser. They may be internal to the PCRF entity or else obtained on thebasis of some other entity, such as the server of the subscribers of thenetwork HSS 28, a DNS domain names server, an AAA (“Authentication,Authorization, Accounting”) entity, the latter being in charge of theprocess for controlling and managing accesses of users to a network,etc.

An item relating to the user equipment can also be taken into accountwhen choosing the other access gateway P-GW2 20. As indicatedpreviously, this may be an item relating to a location of the userequipment, an item relating to user equipment subscription data or elsean item relating to a type of the user equipment.

In an optional manner, when the address of the attachment gateway S-GWhas not been provided by the access gateway P-GW1 in the message O1 a,the PCRF entity 24 can also obtain during this step E2 in particular thecurrent access node, by interrogating the server HSS 28 or the AAAentity. The current access node can be a mobility management entity MME12 or else SGSN 10 or else an attachment gateway S-GW 16 for an accessnetwork of 3GPP type (E-UTRAN, UTRAN, GERAN). The current access nodecan be of any type for a non-3GPP access network.

The PCRF entity 24 then transmits a message O1 b “Acknowledge of IP-CANSession Modification” to the access gateway P-GW1 22. This message O1 bcomplies with 3GPP standard TS 23.203 v8.11.0, paragraph 7.4.1.

According to the invention, the PCRF entity 24 triggers the creation ofthe new IP-CAN session. For this purpose, the PCRF entity 24 transmits amessage O2 “IP-CAN Session Creation Request” destined for the otheraccess gateway P-GW2 20. This message O2 comprises the followingelements:

the address in the network of the attachment gateway S-GW;

a public identifier of the user equipment, for example the MSISDNnumber, for “Mobile Subscriber ISDN Number”;

the determined APN data network identifier.

The access gateway P-GW2 20 receives the message O2 “IP-CAN CreationRequest” in a step F1. As a function of the type of access network,E-UTRAN or GERAN/UTRAN, the access gateway P-GW2 20 will initiatedifferent procedures, represented in the form of a single block “P-GWInit PDN Connectivity” in FIG. 4.

When the access network is of E-UTRAN type, the access gateway P-GW2 20commands establishment of the new session as described in conjunctionwith FIG. 3a . More precisely, the access gateway P-GW2 20 transmits amessage M1 “PDN Connectivity Request” to the attachment gateway S-GW 16whose address was transmitted in the message O2. The various exchangesof message and steps are implemented such as described in conjunctionwith FIG. 3a . The sub-steps E21 of determining the APN data networkidentifier and E23 of determining another access gateway are notimplemented at the level of the mobility management entity MME 12, giventhat they have already been determined by the PCRF entity.

When the access network is of GERAN/UTRAN type, the access gateway P-GW220 commands establishment of the new session as described in conjunctionwith FIG. 3b . More precisely, the access gateway P-GW2 20 transmits amessage N1 “PDN Connectivity Request” to the attachment gateway S-GW 16whose address was transmitted in the message O2. The various exchangesof message and steps are implemented such as described in conjunctionwith FIG. 3b . The sub-steps E21 of determining the data networkidentifier and E23 the access gateway are not implemented at the levelof the mobility management entity SGSN 10, given that they have alreadybeen determined by the PCRF entity 24.

Once the new session has been created, the access gateway P-GW2 20transmits a message O3 “IP-CAN Session Creation Response” destined forthe PCRF entity 24.

On completion of these various steps and exchanges of message, the newsession is established between the user equipment UE 1 and the accessgateway P-GW2 20 in conjunction with the APN data network identifier.The access gateway P-GW2 20 has been selected as a function of thespecific indicator, more precisely the service requested, and ifappropriate, also as a function of items relating to the user equipmentUE. The establishment of the new session has been initiated by the userequipment but by command of one of the entities of the network, moreprecisely in this second embodiment by command of the mobilitymanagement entity SGSN/MME triggered by a request of the PCRF entity 24.

FIG. 5 describes the exchanges between the various facilities for theimplementation of the communication method according to the thirdembodiment, in the case of an E-UTRAN access network.

As described previously in conjunction with FIG. 1, an applicationserver AF 26 receives data packets originating from the mobile entity UE1 by way of the access gateway P-GW1 by means of the established sessionand provides the PCRF entity 24 with items relating to the service in amessage Q1 “Application/service Info”. This message Q1 comprises inparticular items relating to the user equipment, such as the publicMSISDN number, an address in the network of the user equipment.

The message Q1 is received by the PCRF entity during step E1. Stillduring step E1, the PCRF entity 24 detects the request for access to theservice on the basis of the message Q1 and determines that a new sessionmust be created. It is stressed that in this third embodiment, thedetection step is implemented indirectly on the basis of at least onedata packet. The PCRF entity 24 acknowledges the message Q1 through amessage Q2 “Ack” destined for the application server AF 26.

During step E2 previously described in conjunction with FIG. 1, the PCRFentity 24 correlates the policies control rules with the IP-CAN sessionand the specific indicator.

The PCRF entity 24 detects that the session between the user equipmentUE 1 and the access gateway P-GW1 22 is not suitable and decides toestablish a new IP-CAN session. On the basis of data associated with theservice, the PCRF entity 24 determines as a function of the specificindicator the most suitable access gateway, in the example describedhere the other access gateway P-GW2 20, and an APN data networkidentifier. The PCRF entity 24 also verifies the subscription dataassociated with the user.

An item relating to the user equipment can also be taken into accountwhen choosing the other access gateway P-GW2. As indicated previously,this may be an item relating to a location of the user equipment, anitem relating to user equipment subscription data, or else an itemrelating to a type of the user equipment.

The creation of the new session is then implemented in a manneranalogous to what was described in conjunction with FIG. 4, by exchangeof messages Q3 “IP-CAN Session Creation Request” and Q4 “IP-CAN SessionCreation Response”.

On completion of these various steps and exchanges of message, the newsession is established between the user equipment UE 1 and the accessgateway P-GW2 20 in conjunction with the APN data network identifier.The access gateway P-GW2 20 has been selected as a function of thespecific indicator and if appropriate, also as a function of itemsrelating to the user equipment UE 1. The establishment of the newsession has been initiated by the user equipment but triggered by one ofthe entities of the network, more precisely in this third embodiment bycommand of the mobility management entity SGSN/MME triggered by arequest of the PCRF entity 24.

It is stressed here that the descriptions of these second and thirdembodiments have been carried out in the particular case where the PCEFpolicies application function is implemented by the data network accessgateway. They are also transposable in the particular case of an optionof the standard, in which a facility called TDF, for “Traffic DetectionFunction”, is external to the network access gateway.

The embodiments described in conjunction with FIGS. 3a, 3b , 4 and 5envisage the implementation of sub-step E21 of determining a datanetwork identifier. It is recalled that this sub-step E21 is optional,as described previously.

The embodiments described in conjunction with FIGS. 3a, 3b envisage thatsub-step E23 of determining another access gateway is implemented onreceipt of the request regarding establishment of the new sessionoriginating from the user equipment. It is recalled that this sub-stepE23 can be implemented on receipt of the establishment requestoriginating from the gateway for access to the network, jointly withsub-step E21 if the latter is implemented.

FIGS. 6a, 6b, 6c represent in a simplified manner entities of thecommunication network. For the sake of clarity, only the elements of theentities necessary for the understanding of the invention arerepresented.

A first entity 100 is represented in FIG. 6a . It comprises inparticular:

a communication module 101, designed to communicate with the otherentities of the network;

a detection module 102, designed to detect a request for access to aservice on the basis of at least one packet transmitted by the userequipment by means of the established session;

a determination module 103, designed to determine as a function of atleast one criterion that a new session has to be established and totrigger establishment of a new session.

Such a first entity 100 corresponds to an access gateway P-GW1 accordingto the first and second embodiments.

A mobility management entity 200 is represented in FIG. 6b . Such anentity comprises in particular:

a communication module 201, designed to communicate with the otherentities of the network;

a communication module 202, designed to communicate with the userequipment by way of entities of the access network.

The communication module 202 is in particular designed to command theuser equipment regarding establishment of a new session and to establisha session between the user equipment and an access gateway.

In the first embodiment, the mobility management entity 200 furthermorecomprises:

a determination module 203, designed to determine another access gatewaysuitable for the service requested by the user equipment.

Optionally, the determination module 203 is also designed to determinean APN data network identifier.

The first entity 100 cooperates in particular with the mobilitymanagement entity 200 of the communication network to implement thecommunication method described previously according to the firstembodiment.

A PCRF entity 300 is represented in FIG. 6c and comprises in particular:

a communication module 301, designed to communicate with the otherentities of the network;

a determination module 302, designed to determine another access gatewaysuitable for the service requested by the user equipment;

a triggering module 303, designed to trigger establishment of a newsession between the user equipment and another determined accessgateway.

The first entity 100 cooperates in particular with the PCRF entity 300so as to implement the communication method described previouslyaccording to the second embodiment. The PCRF entity 300 cooperates withthe other access gateway P-GW2 so as to implement the communicationmethod described previously according to the third embodiment, inparticular so as to trigger the establishment of the new session by themobility management entity MME/SGSN.

Optionally, the determination module 302 is also designed to determinean APN data network identifier.

According to the third embodiment, the PCRF entity 300 furthermorecomprises:

a detection module 304, designed to detect a request for access to aservice on the basis of a message transmitted by the application serverAF 26, whose emission is triggered by the receipt of at least one packettransmitted by the user equipment by means of the established session;

another determination module 305, designed to determine as a function ofat least one criterion that a new session has to be established.

The PCRF entity 300 cooperates in particular with the other gatewayP-GW2 so as to implement the communication method described previouslyaccording to the third embodiment, in particular so as to trigger theestablishment of the new session by the mobility management entityMME/SGSN.

The user equipment UE 1 also comprises according to the invention meansdesigned to receive a command regarding establishment of the new sessionand to process this command. More precisely, in the case of an E-UTRANaccess network, these means are designed to receive an establishmentcommand message “Request PDN Connectivity”, transmit in response to thiscommand message a session establishment request message “PDNConnectivity Request” to establish the new session, receive a message“PDN Connectivity Accept” indicating that the establishment is on theinitiative of the network and borne by a message “RRC ConnectionReconfiguration”, update an association between the service requestedand a medium as a function of the messages received and transmit amessage “RRC Connection Reconfiguration Complete”. In the case of aGERAN/UTRAN access network, these means are designed to receive anestablishment command message “Request PDP Context Activation” emittedon the initiative of the network, update an association between theservice requested and a medium as a function of the messages receivedand transmit in response to the command message a message “Activate PDPContext Request”.

The invention also relates to a system 3 of the packet modecommunication network, designed to establish at least one sessionbetween at least one user equipment and a gateway for access to a datanetwork by way of a radio access network. This system comprises:

a module 102, 304 for detecting a request for access to a service on thebasis of at least one packet transmitted by the user equipment by meansof the established session;

a first determination module 103, 305, designed to determine as afunction of at least one criterion that a new session has to beestablished;

a second determination module 203, 302, designed to determine anotheraccess gateway suitable for the service requested by the user equipment;

a communication module 202, designed to communicate with the userequipment, in particular to dispatch a command regarding establishmentof a new session to the user equipment and to establish a sessionbetween the user equipment and an access gateway, the said userequipment initiating the establishment of the new session.

The various modules of an entity 100, 200, 300 are designed to implementthose steps of the previously described communication method that areexecuted by the entity. These are preferably software modules comprisingsoftware instructions for executing those steps of the previouslydescribed communication method that are implemented by an entity of thecommunication network. The invention therefore also relates to:

a program for entity, comprising program instructions intended tocommand the execution of those steps of the previously describedcommunication method which are executed by said entity, when saidprogram is executed by a processor of the latter;

a recording medium readable by an entity on which the program for entityis recorded.

The software modules can be stored in or transmitted by a data medium.The latter can be a hardware storage medium, for example a CD-ROM, amagnetic diskette or a hard disk, or else a transmission medium such asan electrical, optical or radio signal, or a telecommunication network.

The invention claimed is:
 1. A method of communication in a packet modecommunication network between a user equipment and a first data network,a session having been established between said user equipment and afirst access gateway for access to the first data network by way of anaccess network, said method comprising: a step of detecting a requestfor access to a new service on the basis of at least one packettransmitted by the user equipment by using the established session; astep of determining as a function of an identifier of the new servicethat a new session has to be established; a step of dispatching to theuser equipment a message commanding the establishment of the new sessionand comprising a data network identifier and the identifier of the newservice, triggering establishment of the new session destined for asecond data network identified by the data network identifier, said userequipment initiating the establishment of the new session; a step ofdetermining a second access gateway, said second access gateway beingsuitable for the new service and selected as a function of theidentifier of the new service; and a phase of establishing the newsession initiated by the user equipment in response to the messagecommanding the establishment of the new session, on completion of whichthe new session is established between said user equipment and saidsecond access gateway, selected as a function of the new service.
 2. Thecommunication method as claimed in claim 1, in which the detection stepis implemented by inspection of a packet stream associated with saidsession.
 3. The communication method as claimed in claim 1, in which thesecond access gateway is also determined as a function of at least oneitem relating to the user equipment.
 4. The communication method asclaimed in claim 3, in which said item belongs to the group consistingof an item relating to a location, an item relating to subscriptiondata, and a type of user equipment.
 5. The communication method asclaimed in claim 1, in which one of said first access gateway or saidsecond access gateway transmits a request regarding establishment of thenew session to a mobility management entity.
 6. The communication methodas claimed in claim 5, in which the first access gateway implements thedetection step and the step of determining that a new session has to beestablished and transmits to the mobility management entity the requestregarding establishment of the new session, said mobility managemententity then implementing the step of dispatching the message commandingthe establishment of the new session and the step of determining asecond access gateway.
 7. The communication method as claimed in claim1, in which, with the communication network comprising entities forcontrolling network policies and charging, the detection step and thestep of determining that a new session has to be established areimplemented by an entity applying network policies; and an entityproviding the network policies determines the second access gateway andtransmits to said second access gateway the request for triggeringestablishment of the new session on the initiative of the userequipment.
 8. The communication method as claimed in claim 1, in whichthe data network identifier is an Access Point Name (APN) identifier. 9.A system in a packet mode communication network, designed to establishat least one session between at least one user equipment and a firstaccess gateway for access to a first data network by way of an accessnetwork, said system comprising: means for detecting a request foraccess to a new service on the basis of at least one packet transmittedby the user equipment by using the established session; firstdetermination means for determining as a function of an identifier ofthe new service that a new session has to be established; communicationmeans for dispatching to the user equipment a message commanding theestablishment of the new session and comprising a data networkidentifier and the identifier of the new service, triggeringestablishment of the new session destined for a second data networkidentified by the data network identifier, and to establish the newsession between the user equipment and a second access gateway, saiduser equipment initiating the establishment of the new session inresponse to the message commanding the establishment of the new session;and second means for determining a second access gateway, said secondaccess gateway being suitable for the new service and selected as afunction of the identifier of the new service.
 10. The system as claimedin claim 9, in which the user equipment is configured to receive themessage commanding the establishment of the new session and to processsaid message.
 11. A hardware storage medium comprising a computerprogram recorded thereon and comprising instructions for implementing acommunication method, when this program is executed by a processor,wherein the method is performed in a packet mode communication networkbetween a user equipment and a first data network, a session having beenestablished between said user equipment and a first access gateway foraccess to the first data network by way of an access network, saidmethod comprising: a step of detecting a request for access to a newservice on the basis of at least one packet transmitted by the userequipment by using the established session; a step of determining as afunction of an identifier of the new service that a new session has tobe established; a step of dispatching to the user equipment a messagecommanding the establishment of the new session and comprising a datanetwork identifier and the identifier of the new service, triggeringestablishment of the new session destined for a second data networkidentified by the data network identifier, said user equipmentinitiating the establishment of the new session; a step of determining asecond access gateway, said second access gateway being suitable for thenew service and selected as a function of the identifier of the newservice; and a phase of establishing the new session initiated by theuser equipment in response to the message commanding the establishmentof the new session, on completion of which the new session isestablished between said user equipment and said second access gateway,selected as a function of the new service.
 12. A user equipment devicecomprising: means for transmitting a packet comprising a request foraccess to a new service, in a packet mode communication network, by wayof an access network, in a first session established between said userequipment and a first access gateway to a first data network; means forreceiving a message commanding establishment of a new session andcomprising a data network identifier and an identifier of the newservice, triggering establishment of the new session destined for asecond data network identified by the data network identifier; means forprocessing said message commanding the establishment of the new session,which initiates establishment of the new session in response to saidmessage commanding the establishment of the new session, between saiduser equipment and a second access gateway, suitable for the new serviceand selected as a function of the identifier of the new service.